Re: Ultramatic transmission problems

Posted by humanpotatohybrid On 2023/11/17 17:11:24

To add detail to Ross's response, the torque converter is composed principally of a driving and driven turbine, each radially vaned. When filled with fluid and spun, the vanes push the fluid in a circular path around the turbine (rotary flow), and hence the resulting centrifugal force draws the fluid from the center to the extremity of each turbine. Whichever spins faster, the fluid has more centrifugal force, and so will drive the other; likewise, the amount of fluid transfer between the two is heavily related to the difference in their rotary speed. Generally this difference is highest on initial acceleration, so there is a great velocity of fluid flowing from the center to the extremity of the driving turbine then into the extremity of the driven one (vortex flow); however, the momentum of the rotary flow (the flow in the direction of turbine rotation) is not great, and the torque transmitted is not satisfactory by this arrangement alone. To correct this deficiency, the torque converter has two additional turbines, which combined, utilize most of the remaining energy in the vortex flow to convert it to additional torque (hence the name "torque converter"). The fluid, because of the reaction force of flying through the (first) driven turbine, actually is afterwards flowing in the opposite corkscrew direction as what could drive another turbine in the correct direction. So, it flows through a "reactor" turbine (so named because it provides a reaction force) whose blades reverse the corkscrew direction of the fluid after which it directly flows into the second turbine which, being directly connected to the first driven turbine, provides additional torque to the output shaft.

At higher car speeds the difference in rotary speeds of the two halves of the torque converter is minimal, so the effects of the reactor are not needed, and it is most beneficial overall for the reactor to spin with the other parts (with the fluid). This is why it has a sprag clutch, to automatically engage or disengage when needed. Simply put, when the reactor is needed, the fluid flow is such that it tries to turn the reactor in the locking direction, which locks up the clutch. When it is not needed, it tends to rotate in the direction opposite. If the reactor can't lock up, then the torque multiplication is minimal to negative, negative meaning that the reactor not being able to help makes the second turbine a detriment rather than a benefit to the torque output.

I imagine that the sprag clutch slips when the reactor is changing direction at velocity, but when the transmission fluid and parts settle down with the engine off, it is able to settle in a bit and grip sufficiently to get going.

Be sure your mechanic scribes the necessary areas when disassembling the converter.

Read page 2 of the manual for diagrams and more detail:https://packardinfo.com/xoops/html/downloads/servicemanual5556/Sect07_TwinUltra.pdf